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Commit 1983f9b0 authored by Greg Kaiser's avatar Greg Kaiser
Browse files

ContextHubService: Hack around 32-bit app ID 

The NanoApp.java class has a bug (b/30808791) where the API treats
app IDs as 32-bits, instead of 64-bits.  We are too late in the
Android N release cycle to change this API.

We previously put in a hack to fix this only for Google nanoapps.
However, our GTS nanoapps need this to work, and there are other
partners who need this to work in the N timeframe.  So we make
a more robust hack which parses the full 64-bit app ID out of
the header binary.

Test: Compiles and runs GTS
Bug: 31767599
Change-Id: Ic43f1f62c685fb99aac08d08767d1a67c329503f
parent c8dd22bc

core/java/android/hardware/location/ContextHubService.java

+35 −16
Original line number Diff line number Diff line
@@ -18,6 +18,8 @@ package android.hardware.location; 


import java.io.FileDescriptor;

import java.io.PrintWriter;

import java.nio.ByteBuffer;

import java.nio.ByteOrder;

import java.util.ArrayList;

import java.util.HashMap;
@@ -146,6 +148,36 @@ public class ContextHubService extends IContextHubService.Stub { 
        return mContextHubInfo[contextHubHandle];

    }



    // TODO(b/30808791): Remove this when NanoApp's API is correctly treating

    // app IDs as 64-bits.

    private static long parseAppId(NanoApp app) {

        // NOTE: If this shifting seems odd (since it's actually "ONAN"), note

        //     that it matches how this is defined in context_hub.h.

        final int HEADER_MAGIC =

            (((int)'N' <<  0) |

             ((int)'A' <<  8) |

             ((int)'N' << 16) |

             ((int)'O' << 24));

        final int HEADER_MAGIC_OFFSET = 4;

        final int HEADER_APP_ID_OFFSET = 8;



        ByteBuffer header = ByteBuffer.wrap(app.getAppBinary())

            .order(ByteOrder.LITTLE_ENDIAN);



        try {

            if (header.getInt(HEADER_MAGIC_OFFSET) == HEADER_MAGIC) {

                // This is a legitimate nanoapp header.  Let's grab the app ID.

                return header.getLong(HEADER_APP_ID_OFFSET);

            }

        } catch (IndexOutOfBoundsException e) {

            // The header is undersized.  We'll fall through to our code

            // path below, which handles being unable to parse the header.

        }

        // We failed to parse the header.  Even through it's probably wrong,

        // let's give NanoApp's idea of our ID.  This is at least consistent.

        return app.getAppId();

    }



    @Override

    public int loadNanoApp(int contextHubHandle, NanoApp app) throws RemoteException {

        checkPermissions();
@@ -162,27 +194,14 @@ public class ContextHubService extends IContextHubService.Stub { 
        msgHeader[HEADER_FIELD_MSG_TYPE] = MSG_LOAD_NANO_APP;



        long appId = app.getAppId();

        // TODO(b/30808791): Remove this hack when the NanoApp API is fixed.

        // Due to a bug in the NanoApp API, only the least significant four

        // bytes of the app ID can be stored.  The most significant five

        // bytes of a normal app ID are the "vendor", and thus the most

        // significant of the bytes we have is the least significant byte

        // of the vendor.  In the case that byte is the ASCII value for

        // lower-case 'L', we assume the vendor is supposed to be "Googl"

        // and fill in the four most significant bytes accordingly.

        // TODO(b/30808791): Remove this hack when the NanoApp API is fixed,

        //     and getAppId() returns a 'long' instead of an 'int'.

        if ((appId >> 32) != 0) {

            // We're unlikely to notice this warning, but at least

            // we can avoid running our hack logic.

            Log.w(TAG, "Code has not been updated since API fix.");

        } else {

            // Note: Lower-case 'L', not the number 1.

            if (((appId >> 24) & 0xFF) == (long)'l') {

                // Assume we're a Google nanoapp.

                appId |= ((long)'G') << 56;

                appId |= ((long)'o') << 48;

                appId |= ((long)'o') << 40;

                appId |= ((long)'g') << 32;

            }

            appId = parseAppId(app);

        }



        msgHeader[HEADER_FIELD_LOAD_APP_ID_LO] = (int)(appId & 0xFFFFFFFF);